The growth of 'Dry January': promoting participation and the benefits of participation.

This article explores contributors to the rapid growth of the annual UK alcohol abstinence challenge 'Dry January' and the benefits of registration. Evidence from four sources is presented: (i) registrations via the Dry January website, (ii) surveys of population-representative samples of drinkers, (iii) surveys of Dry January registrants and (iv) surveys of a control group of drinkers who wanted to change to their drinking behaviour but had not registered for Dry January. The data revealed that Dry January registrations increased 15-fold in 4 years. Participants reported that encouragement received from Dry January helped them to avoid drinking. Comparisons of Dry January registrants to the control group suggest that registering for Dry January reduced problematic drinking and enhanced the capacity to refuse alcohol. The four sources of data suggest that 'social contagion' and 'diffusion' have aided the growth of the awareness, appeal and practice of Dry January.